()60 



BURGESS AND KELLBERG: ALLOTROPY OF COPPER 



3. In a third series, the platinum and copper resistances were 

 measured separately with a common lead and a common battery 

 lead, (as in the observations on iron) and the times taken to 0.1 

 second on a chronograph. For this series a new length of pre- 

 viously annealed copper wire was used which also received the 

 preliminary alternate heating and cooling shown in Table I. 



TABLE II 



Measurements op Copper Resistance 



The thermometer leads were of gold for the third series and of 

 copper for the other two. The Wheatstone bridge used was one 

 specially designed for calorimetric work^ and, as used, accurate 

 and sensitive to 1 in 500,000. Observations were taken every 



« lUiUetin Bureau of Standards 11; 571. 1915. 



